Tube bending is known in the art and typically involves bending an elongated metal tube with a rotary die. As the tube is bent around the draw die, the tube undergoes an abrupt change from a straight tube with curvature equal to zero in its axial direction to a tube with positive and constant curvature of the circular bend. The abrupt change causes a portion of the tube contacting the surface of the die to compress, while a portion of the tube opposite the surface of the die stretches. As a result, the bending can create folds or oscillations on the bent portion of the tube.
Bending a tube around a draw die may also deform cross sections of the tube to non-circular shapes. To prevent deformation of the tube, a mandrel is inserted into the tube to reinforce the wall of the tube and help prevent the tube from becoming deformed. However, using a mandrel to prevent tubular deformation can present difficulties, since the bent portion of the tube may pinch the mandrel and create difficulties in removing the mandrel.